Hiroyuki Haraguchi

Antioxidative and superoxide scavenging activities of retrochalcones in Glycyrrhiza inflata

Licochalcone A, B, C, D and echinatin, retrochalcones isolated from the roots of Glycyrrhiza inflata (licorice), along with an ordinary chalcone isoliquiritigenin, were assessed for their inhibitory activities on lipid peroxidation in various systems and radical scavenging activity. Among those tested, licochalcones B and D strongly inhibited superoxide anion production in the xanthine/xanthine oxidase system. These two compounds also showed potent scavenging activity on DPPH radical. Microsomal lipid peroxidation induced by Fe(III)-ADP/NAPDH was inhibited almost completely by 3 micrograms/ml of licochalcones B and D. Mitochondrial lipid peroxidation induced by Fe(III)-ADP/NADH was more sensitive to these retrochalcones; almost complete inhibition was observed at 10 micrograms/ml of all retrochalcones tested. Licochalcones B and D scavenged superoxide anion in microsome. Furthermore, these retrochalcones protected red cells against oxidative hemolysis. These phenolic compounds were shown to be effective to protect biological systems against various oxidative stresses.

Mode of antibacterial action of retrochalcones from Glycyrrhiza inflata

Licochalcone A-D and echinatin, retrochalcones isolated from the roots of Glycyrrhiza inflata, showed antimicrobial activity. Among them, licochalcone A and C had potent activity against some Gram-positive bacteria. These retrochalcones inhibited oxygen consumption in susceptible bacterial cells. The oxidation of NADH in bacterial membrane preparations was also inhibited by them. NADH-cytochrome c reductase was inhibited by licochalcones, while cytochrome c oxidase was not. NADH-CoQ reductase and NADH-FMN oxidoreductase were not inhibited. The site of respiratory inhibition of licochalcones was thought to be between CoQ and cytochrome c in the bacterial respiratory electron transport chain.

Protection of mitochondrial functions against oxidative stresses by isoflavans from Glycyrrhiza glabra

Isoflavan derivatives, glabridin (1), hispaglabridin A (2), hispaglabridin B (3), 4′‐O‐methylglabridin (4) and 3′‐hydroxy‐4′‐O‐methylglabridin (5), isolated from Glycyrrhiza glabra, were investigated for their ability to protect liver mitochondria against oxidative stresses.

Antiperoxidative Activity of Neolignans from Magnolia obovata

Honokiol and magnolol, neolignans in Magnolia obovata, have been evaluated as antioxidants.

Antioxidative sulphated flavonoids in leaves of Polygonum hydropiper

Abstract Three hydrophilic flavonoids were isolated and identified from leaves of Polygonum hydropiper as quercetin 3-sulphate, isorhamnetin 3,7-disulphate and tamarixetin 3-glucoside-7-sulphate. The structures were established by chemical and spectral evidence, and their antioxidative activity and effect on the generation of superoxide anion evaluated.

Antimicrobial tetrahydroanthraquinones from a strain of Alternaria solani.

Abstract Culture liquid and mycelia of a strain of Alternaria solani , which was isolated from a diseased Lycopersicon esculentum , afforded new tetrahydr

Altersolanol-related antimicrobial compounds from a strain of Alternaria solani

Abstract Four new altersolanol-related compounds, hydroxybostrycin, altersolanol G, altersolanol H and an atropisomer of alterporriol C, together with a mixture of alterporriol A and alterporriol B, have been isolated from the culture liquid of a strain of Alternaria solani obtained from a diseased Lycopersicon esculentum . Their structures have been established on the basis of spectral and chemical evidence. The structures of altersolanols G and H were shown to be 6-methoxy-1β,3β-dimethyl-2α,3α, 4β,8-tetrahydroxy-1,2,3,4-tetrahydroanthraquinone and 6-methoxy-3β-methyl-2β,3α,4β,8-tetrahydroxy- 1,2,3,4-tetrahydroanthraquinone, respectively.

Inhibition of lipid peroxidation by sesquiterpenoid in Heterotheca inuloides

A sesquiterpenoid, 7‐hydroxy‐3,4‐dihydrocadalin, isolated from a Mexican medicinal plant Heterotheca inuloides was evaluated as an antioxidant.

Inhibition of aldose reductase by dihydroflavonols in Engelhardtia chrysolepis and effects on other enzymes.

Astilbin and neoastilbin, dihydroflavonol rhamnosides fromEngelhardtia chrysolepis, showed potent inhibition of lens aldose reductase. Kinetic analysis showed astilbin exhibited uncompetitive inhibition against bothdl-glyceraldehyde and NADPH. These taxifolin glycosides were selective inhibitors of aldose reductase with no inhibition of NADH oxidase.

Mode of phytotoxic action of altersolanols

Abstract Altersolanol A, a phytotoxic tetrahydroanthraquinone isolated from the culture broth of Alternaria solani , inhibited the growth of cultured cells of Nicotiana rustica . It acted as a potent stimulator of NADH oxidation in mitochondria isolated from N. rustica cells. The stimulation was also observed in mitochondria in which the respiratory chain was blocked by electron transport inhibitors. Altersolanols acted as electron acceptors in an enzyme preparation of diaphorase. The capacity of altersolanols to act as electron acceptors was A>E>C>B>F>D.